android 添加水印效果的实现

Bitmap photo = BitmapFactory.decodeResource(r, res);
Bitmap icon = Bitmap.createBitmap(width, hight, Bitmap.Config.ARGB_8888); //建立一个空的BItMap
Canvas canvas = new Canvas(icon);//初始化画布 绘制的图像到icon上

Paint photoPaint = new Paint(); //建立画笔
photoPaint.setDither(true); //获取跟清晰的图像采样
photoPaint.setFilterBitmap(true);//过滤一些

Rect src = new Rect(0, 0, photo.getWidth(), photo.getHeight());//创建一个指定的新矩形的坐标
Rect dst = new Rect(0, 0, width, hight);//创建一个指定的新矩形的坐标
canvas.drawBitmap(photo, src, dst, photoPaint);//将photo 缩放或则扩大到 dst使用的填充区photoPaint

Paint textPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DEV_KERN_TEXT_FLAG);//设置画笔
textPaint.setTextSize(20.0f);//字体大小
textPaint.setTypeface(Typeface.DEFAULT_BOLD);//采用默认的宽度
textPaint.setColor(Color.RED);//采用的颜色
textPaint.setShadowLayer(3f, 1, 1,r.getColor(android.R.color.background_dark));//影音的设置
canvas.drawText(str, 20, 26, textPaint);//绘制上去 字，开始未知x,y采用那只笔绘制